Mediastinum
Thymic carcinoma
Thymic squamous cell carcinoma


Topic Completed: 1 December 2012

Minor changes: 10 June 2020

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PubMed Search: Thymic carcinoma[TI] general


Hanni Gulwani, M.B.B.S.
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Cite this page: Gulwani H. Thymic squamous cell carcinoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/mediastinumthymiccarcinoma.html. Accessed July 4th, 2020.
Definition / general
  • By definition, has overt cellular anaplasia
Epidemiology
  • Ages 50+, occasionally children
Diagrams / tables

Images hosted on other servers:

Proposed stage T1, tumor limited to thymic gland

Proposed stage T2, tumor invades nearby structures

Proposed stage T3, direct (continuous) extrathoracic tumor extension beyond thoracic inlet or below diaphragm

Clinical features
  • Associated with hypercalcemia, elevated parathyroid hormone levels, pulmonary sarcoidosis
  • Not associated with paraneoplastic syndromes such as myasthenia gravis or pure red cell aplasia
  • Patients usually present with mass related symptoms
  • Aggressive clinical course
  • Must exclude other primaries, which are much more common (lung, trachea, bronchi, esophagus)
  • Usually squamous cell carcinoma and variants (lymphoepithelioma-like, basaloid)
  • Proposed staging system (Am J Clin Pathol 2012;138:115)
Radiology images

Contributed by Dr. Lina Hu, for Case of the Month #479:

Mass with irregular, infiltrative borders

Prognostic factors
  • May be less aggressive than commonly believed; important prognostic factors are lymph node status and tumor size (Am J Clin Pathol 2012;138:103)
  • Keratinizing: good prognosis with few fatalities if well differentiated
Case reports
Gross description
  • Unencapsulated, no internal fibrous septation, firm / hard / gritty with gray-white cut surface, necrosis and hemorrhage
Microscopic (histologic) description
  • Usually cohesive cellular growth, regularly round / oval nuclear outlines, eosinophilic nucleoli, geographic necrosis
  • Usually foci of medullary differentiation, abortive Hassall corpuscles, rosettes, gland-like spaces, T lymphocytes; no perivascular spaces
  • Keratinizing:
    • Similar to tumor in skin, lung, other sites
    • Lobular growth with fibrous bands
    • Nests and cords of large polyhedral cells with intercellular bridges
    • Vesicular or hyperchromatic nuclei, prominent nucleoli, eosinophilic or glassy cytoplasm, keratin pearls
    • Also angiolymphatic invasion, necrosis
    • Rarely coexists with thymoma
  • Non-keratinizing
    • Angular nests of malignant squamous cells in desmoplastic stroma
    • No intercellular bridges, no eosinophilic cytoplasm, no keratin pearls
Microscopic (histologic) images

Contributed by Dr. Lina Hu, for Case of the Month #479:

KIT / CD117

p63

Positive stains
Negative stains
Electron microscopy description
  • Well formed desmosome-like intercellular junctions, cytoplasmic tonofilaments that may insert into junctional complexes
Differential diagnosis
Board review style question #1
Which two antibodies are most helpful in diagnosing thymic carcinoma?

A. CK5/6, 34bE12
B. CD5, p63
C. CEA, synaptophysin
D. p63, p40
E. KIT / CD117, INSM1
Board review answer #1
B. CD5 combined with p63 are helpful thymic markers.
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